1. Field of the Invention
The present invention relates to a piston assembly comprising a piston having an unobstructed annular space for an O-ring and an O-ring received in the unobstructed annular space. The piston assembly is received in a cylinder of a trigger sprayer body and acted upon by a trigger movably mounted to the trigger sprayer body. To form the piston with an unobstructed annular space for receiving an O-ring, the piston is preferably made of two parts which are press-fitted together thereby forming an annular space between the two parts for receiving the O-ring.
2. Description of the Related Art Including Information Disclosed Under 37 CFR .sctn..sctn. 1.97-1.99.
Heretofore, trigger sprayers have been proposed which include a piston comprising a generally cylindrical piston body having a cylindrical cavity opening rearwardly of the piston body and a rubber or elastomeric, cup shaped insert received in the cavity and having on an outer periphery one or two lip seals which are generally frusto-conical in cross-section for engaging and sealing against an inside wall of a cylinder within which the piston is received. A piston of this type is illustrated in FIG. 1.
Such pistons with a cup shaped insert having one or two lip seals, typically made out of a rubber or elastomer have worked well. However, such inserts have been found to be expensive to produce. In this respect, the piston of the type shown in FIG. 1 costs between four and ten cents.
Furthermore, it has been found that a piston having lip seals made out of a rubber is not necessarily suitable for all kinds of liquids, particularly, cleaning fluids which are now being sold in containers having manually operated trigger type sprayers attached thereto for the dispensing cleaning fluid.
It has been known that an O-ring-type seal provides a good deflectable seal for a piston. However, when making a plastic one-piece piston, the molding is typically end to end such that flashing occurs. If an annular space is provide on such a piston for receiving an O-ring, the O-ring often will not make a good seal with the bottom or sides of the annular space for receiving the O-ring because of an axially and/or radially extending ridge caused by the flashing in molding the piston.
As will be described in greater detail hereinafter, the piston assembly of the present invention provides a piston assembly including an unobstructed annular space in a piston body for receiving an O-ring and an O-ring mounted in the annular space thereby providing an inexpensive piston assembly which is less expensive to manufacture and assemble than the present pistons with a lip seal or seals, which can be used with all kinds of liquids, and which provides a sealing member, namely the O-ring, made of different materials.